This invention is to a minimally invasive surgical device. In particular, the invention relates to an infusion catheter which may be used in cardiovascular and endovascular procedures to deliver diagnostic, therapeutic, or vasoocclusive agents to a target site accessible through the vasculature. The device is a flow-directed infusion catheter having a variety of sections of different flexibilities with tapered junctions between those sections. The inventive catheter is directed to that target site by a flow of blood to the site.
As the cost of classical surgery increases and the sophistication of minimally invasive surgical technology improves, the use of catheters as means for delivering diagnostic and therapeutic agents to internal target sites has similarly increased. Of particular interest herein are catheters which may be used to access target sites through the circulatory system.
There are a number of generalized procedures for placing catheters within vessels in the body for accessing sites that are difficult to approach. Specifically, one such technique involves the use of a torqueable guidewire which is alternately rotated and advanced to the target site. As the guidewire is advanced, the catheter is then advanced along the wire until the distal end of the catheter is positioned at the desired target site. An early example of this technique is described in U.S. Pat. No. 4,884,579, to Engelson. Although the technology involved in such a catheter is quite sophisticated, many consider the catheter to be a second choice when a highly time-sensitive situation is to be treated. This is due to the comparatively time-consuming nature of rotating and advancing the guidewire and then advancing the catheter over the guidewire through the vasculature.
Another technique for advancing a catheter to a target site is to employ a highly flexible catheter having an inflatable, but pre-punctured, balloon at its distal end. In use, the balloon is partially inflated, and carried by blood flow to the target site. During such a placement procedure, the balloon is continually inflated to replenish fluid leaking from the balloon. This technique, too, has major drawbacks, including the fact that the catheter material is so flexible that the catheter cannot be pushed from the proximal end without buckling some portion of the catheter. Instead, the catheter must be advanced using injected fluid to inflate the balloon in order to propel the catheter to the target site. There is always the risk of rupture of a vessel by a balloon that has been too highly inflated.
Flow-directed catheters have also been proposed which do not use such leaking balloon technology. Specifically, the catheters are so flexible at their distal and mid regions that they are able to be carried by blood flowing to a target site. Examples of such products are described in U.S. Pat. No. 5,336,205 (to Zenzen et al.) and U.S. Pat. No. 5,538,512 (to Zenzen et al.). These catheters have in common the presence of a relatively stiff tapered proximal segment, a relatively flexible and strong distal segment, and a transition section between those proximal and distal segments which is intermediate in flexibility. The distal segment has a burst pressure release of 195 psi and is made of a material that shows exceptional deflection when a minor force is placed upon such distal portion.
Neither of these patented devices have the structure of the device described below.
This invention is an infusion catheter for placement within the vasculature. In particular, it may be delivered to a target site by means of blood flow to that site. It may be used to deliver diagnostics, therapeutics, or vasoocclusive agents via tortuous, small vessel pathways to the selected site. The infusion catheter has an elongate tubular body having proximal and distal ends and a lumen extending between those ends.
The elongate tubular body is formed of a comparatively stiff proximal segment, a comparatively flexible and fairly strong distal segment, and a transition section between the proximal and distal segments that is intermediate in its flexibility. It may have more segments if such is desired. In general, the proximal segment is of a specific diameter, the midsection is of a smaller constant diameter, and the most distal segment may be of a relatively constant and comparatively smallest diameter. The devices typically have a tapered joint placed between each of the noted segments. Highly preferred is a structure which has been annealed so that the thermoplastics found at the various joints have been smoothed and the crystallinity of the polymers in the various catheter segments has been lessened.
The materials preferably making up the various catheter segments are desirably thermoplastics, particularly polyvinylchloride (PVC) or polyurethane. Also desirably, the polymers may contain a radio-opacifier such as bismuth subcarbonate. Each of the segments may contain this radio-opacifier additive but is especially preferred that it be placed in the distal and middle segments. Finally, it is highly desirable that the catheter assembly be of such flexibility that it be combined with a stylet for delivery in a guiding catheter to a region of the body through a larger guiding catheter. Once the distal end of the inventive catheter is near the distal end of the guide catheter, the stylet is removed and only then is the blood flow used to extend the inventive catheter to its target site.
The interior and exterior of the device may be coated with a hydrophilic coating.